During the drilling of an oil and gas well, long strings of pipe are strung together to form a drill string or to form a casing string to line the well bore. These pipe strings are usually supported by rotary spiders that fit into or over the opening of a rotary table on the drilling rig. Spiders typically employ slips that are peripherally distributed around the perimeter of the central opening of an inwardly tapered slip bowl. The slips are typically fitted with detachable dies having a plurality of teeth which form a pipe gripping surface to increase the grip of the slips on the pipe string.
Spider slips are typically attached to a slip timing ring by a linkage so that upward and downward movement of the slip timing ring will simultaneously move the slips upward and downward in the slip bowl for engaging and releasing the pipe string. Hydraulically or pneumatically powered cylinders having extendable and retractable pistons and rods are typically used to raise and lower the slip timing ring. Retraction of the cylinder piston rods moves the timing ring and thus the slips downward so that the inwardly tapered slip bowl surface will urge the downwardly moving slips radially inward to bear upon and grip the pipe. Extension of the cylinder piston rods moves the timing ring and thus the slips upward in the tapered slip bowl so that the upwardly moving slips move radially outward away from the pipe string in order to release the pipe.
Ordinarily a spider should have the lowest possible elevation profile with respect to the top of the rotary table. A spider with a low elevation profile allows a worker to work at a more convenient height above the top of the rotary table and a low spider elevation profile provides less interference from the spider during the manipulation of tongs and other pipe handling equipment. However, as wellbore depth increases pipe strings become longer, heavier, and are made of pipe of larger diameters, necessitating the need of a high capacity spider. In a typical high capacity spider, the central opening for the pipe of a high capacity spider is restricted by the size of the slips required to retain the pipe string load and the diameter of the pipe collars ultimately limiting the size of the pipe and the length of the pipe string. Consequently, there is a need for a flush mounted rotary table spider that provides workers with room to work while maximizing the usable space in central opening of the spider to allow pipe collars to pass without interference.